I'm working on a project replacing my floor and stringers. I know external plywood is the recommended option but the stuff I saw at Lowes was BC, had only 4 plys, and large voids everywhere. However, they had oak hardwood plywood. It looks like it had about 10 plys of oak, was sanded smooth, and any voids were very small. It seems like the better choice but the sign says for interior applications only. Does that mean the glue holding it together won't hold up to water? If the stringers are coated in poly and encased in fiberglass is that still an issue?
